C96 SYSTEMATIC BOTANY. 



Ampliibolis, Zostera. There are about 12 species. Their pro- 

 perties are of little importance. 



Zostera marina, Sea-wrack, is in common use for packing, and for 

 stuffing chairs, mattresses, &c., under the name of Alva (Ulva or Ah/a) 

 marina. It has also been recommended for paper -making, but it is a 

 very unsuitable material for that purpose. 



Natural Order 279. Tritjeidace^. — The Triuris Order. — 

 Diagnosis. — This is a small order of plants closely allied to 

 Naiadacese, but usually to be distinguished by its rudimentary 

 embryo. The flowers are, laowever, sometimes perfect. 



Bistrihutio'n, ^-c. — Exclusively found in warm and tropical 

 regions. — Examples of the Genera : — Triuris, Sciaphila. There 

 are 8 species. Their properties and uses are unknown. 



Natural Order 280. Hydjrogharidace^. — The Hydrocharis 

 or Frog-bit Order. — Character. — Aquatic plants. Flowers 

 spathaceous, regular, dioecious or polygamous. Perianth supe- 

 rior, in 1 or 2 whorls, each of 3 pieces, the inner petaloid. 

 Stamens few or numerous. Ovary inferior, 1 — 9-celled. Fruit 

 indehiscent. Seals numerous, without albumen. 



Distribution, (Sfc. — Inhabitants of fresh water in Europe, North 

 America, East Indies, and New Holland. Examples of the Ge- 

 nera: — Anacharis, Vallisneria, Hydrocharis. There are about 

 25 species. Their properties are unimportant. 



Natural Order 281. Eestiaceje. — The Eestio Order. — 

 C h a ra c t er. — Herbs or under-shrubs. Leaves simple and narrow, 

 or entirely absent. Stems stiff, either naked, or more commonly 

 with slit equitant leaf-sheaths. Fiowcrs with glumaceous bracts, 

 spiked or aggregated, generally unisexual. No true perianth, 

 its place being usually supplied by glumes. Stamens 2 — 3, 

 adherent to 4 — 6 glumes, or the latter sometimes absent ; anthers 

 generally 1 -celled. Ovary 1 — 3-celled, with 1 pendulous ovule 

 in each cell. Fruit capsular or nut-like. Seeds albuminous, 

 without hairs ; embryo lenticular and terminal. 



Distribution, cfr. — Natives principally of South Africa, South 

 America, and Australia. Some are also found in the tro- 

 pical parts of Asia ; but none occur in Europe. Examples 

 of the Genera: — Leptocarpus, Eestio. There ai-e about 180 

 species. 



Properties and Uses. — Unimportant. The wiry stems of 

 some species have been used for basket-making, &c., and for 

 thatching. 



Natural Order 282. Eriocaulaceje. — The Eriocaulon or 

 Pipe wort Order. — Character. — Aquatic or marsh plants. 

 Leaves clustered, linear, usually grass-like. Flowers minute, 

 unisexual, in dense heads, each flower arising from the axil of a 

 membranous bract. Perianth tubular, 2 — 3-toothed or lobed. 

 Stamens 2— G; anthers 2-celled, introrse. Otwy superior, 2 — 

 3-celled Fruit dehiscent, 2 — 3-celled, 2 — 3-seeded. Seeds 



